Enabling shallow water flight on Slocum gliders

Abstract

Underwater gliders are a disruptive technology capable of transforming our understanding of the ocean. Efficient vehicle flight is critical for proper data collection, allowing successful completion of project goals. Slocum glider flights in less than 15 m of water have been only marginally successful, as use of deep water flight coefficients disables proper inflection at shallow depths. Groundings can damage sensors, degrade data, halt progress, and ultimately endanger the vehicle. To correct poor flight performance, sensor parameters responsible for inflection were individually analyzed and adjusted. Tests were conducted on repeated flights in the shallow state waters of New Jersey with glider RU28 while conducting dissolved oxygen surveys for the New Jersey Department of Environmental Protection (NJDEP) and the United States Environmental Protection Agency (USEPA); further verifications were conducted off the shoaling areas of Delaware with glider OTIS while searching for tagged sturgeon and sand tiger sharks. As a result of these tests, flight performance has been drastically improved, with efficient flight in 8 m of water, including several promising instances in water as shallow as 6 m. Prior to adjustments, gliders would make little forward progress and spend 50-100% of a flight segment grounded. With the new parameters loaded, groundings have been eliminated from coastal missions. Enabling shallow water flight for Slocum gliders allows vehicle operations in an area largely unexplored by this type of platform, opening up coastal areas to new project ideas and sampling schemes. Shallow water flight parameters can be shared with the community to increase sampling density in areas previously off limits to these vehicles.